Inform user about automatic comment closing time

To prevent spammers from flooding old articles with useless comments you can set WordPress to close comments after a certain number of days:
It might be surprising for some users if the comments are closed automatically so it might be a good idea to inform them about the remaining time.

While the code should be almost self explanatory there is an interesting function not every WordPress developer might know: human_time_diff(). This function is hidden in the .../wp-includes/formatting.php file. It is originally planned to be used in themes to provide a more "human" touch to the date/time a post was written. Since the function does not care if the date is in the past or in the future we can use it for our needs.